This invention relates to electronic musical instruments, and, more particularly, to an electronic circuit for use in an electronic organ for simulating a string bass sound.
The timbre or tonal qualities of the sounds generated by an electronic organ are conventionally achieved by producing an audio frequency signal of the particular wave shape which when reproduced by a loudspeaker produces the desired tonal quality, one common system being characterized as of the "formant" type which starts with a pulse wave shape, for example a rectangular pulse or sawtooth pulse, and uses various filters to attenuate or emphasize desired harmonic frequencies to achieve an audio frequency signal of desired wave shape. U.S. Pat. No. 3,316,341, for example, describes the use of a dynamic filter, a tuned resonant filter that peaks certain frequencies in the audio frequency spectrum and attentuates others, both above and below the frequency to which the filter is tuned, for introducing dynamic variations, under player control, in the tone quality of an electrical musical instrument. Many other specific combinations of starting wave shape and filters of different characteristics are known for producing particular sounds, but applicant is unaware of any system for economically electrically producing a wave shape which when reproduced by a loudspeaker produces a sound simulative of a plucked string bass sound. Analysis has revealed that the sound signal immediately following plucking contains many high order harmonics and thereafter the sound dies away with a relatively long time constant toward a substantially pure fundamental sound, having few or any significant harmonics.
It is a primary object of the present invention to provide an electronic circuit for economically producing an electrical signal which when reproduced simulates the sound of a plucked string bass.